10 gallons is only just enough tank space for one goldfish, you won't be able to have any more fish in that tank I'm afraid, otherwise it will get over crowded.

If your husband would like tropical fish, you could always get a new tank for that Tropical fish need warm water and will require a heater because of this, whereas goldfish are quite happy being kept in cold water tanks. So generally the two are best kept apart and not mixed together.

I agree with Skwishee. No more fishies for a tank that size, unless you have a 10 gallon with only tropicals in it. Goldfish and tropical fish do not usually go together too well because they have different heating requirements (as they like much warmer water that goldies, which are cold-water fish) and are known to pick on the peaceable goldfish. This causes stress and irritation on part of the goldfish, so it's best to just leave that little fishy by himself in that 10 gallon. You will also discover very quickly that goldfish grow FAST and BIG. As in, 6-8 inches for fancies and 12 inches + for single tailed varieties.

If I were you, I'd get a 20 gallon for the goldfish and make the 10 nice and cozy for some tropicals... Like the other posters said, they're not compatible because of their water quality requirements. Most tropicals want soft and acidic water while goldfish want the opposite, aside from the temperature difference.